<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width, initial-scale=1">
  <title>Animating pseduo-element on scroller</title>
</head>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src="/web-animations/testcommon.js"></script>
<script src="./support/testcommon.js"></script>
<script src="testcommon.js"></script>
<style type="text/css">
.scroller {
  overflow: auto;
  width: 100px;
  height: 100px;
  margin: 1em;
  outline: 1px solid;
  animation: bg linear;
  animation-timeline: scroll(self inline);
}
.pseudo::before {
  content: "";
  display: block;
  width: 200px;
  height: 50px;
  background: red;
  animation: bg linear reverse;
  animation-timeline: scroll(inline);
}
@keyframes bg {
  from {
    background: rgb(0, 255, 0);
  }
  to {
    background: rgb(0, 0, 255);
  }
}
</style>
<body>
  <div class="scroller pseudo"></div>
  <div id="log"></div>
</body>
<script type="text/javascript">
  'use strict';

  promise_test(async t => {
    await waitForCSSScrollTimelineStyle();
    const scroller = document.querySelector('.scroller');
    assert_equals(getComputedStyle(scroller).backgroundColor, 'rgb(0, 255, 0)');
    assert_equals(getComputedStyle(scroller, ':before').backgroundColor,
                  'rgb(0, 0, 255)');
  }, `scroll nearest on pseudo-element attaches to parent scroll container`);
</script>
</html>
